Non-executable stack

[martinko]

Julian Elischer wrote:
> Dag-Erling Smørgrav wrote:
> 
>> db <db at traceroute.dk> writes:
>>  
>>
>>> Memory on ia32 can be writable and readable.  When it is readable it
>>> is also executable.  On other arch's like AMD64 and IA64, I believe
>>> memory can be readable, writable and executable.
>>>   
>>
>>
>> Not quite.  IA32 can make individual segments readable, writable and /
>> or executable, but lacks the ability to do so on a per-page basis.
>> Since we have trampoline code at the top of the stack, the entire
>> stack segment must be executable.  Moving the trampoline off the stack
>> would solve the problem on all platforms.
>>  
>>
> 
> There has been recent talk of a shared kernel/user memory page..
> that could be used for trampoline code.
> 
>> W^X across the board is not an option - it would break HotSpot and
>> other JIT-based software.
>>
>> DES
>>  
>>
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> 

and what exactly is that trampoline btw/pls ?